Utilization of biochemical light-sensitizing extracts in the art of photographic materials



Patented Oct. 12, 1926.

UNITED, STATES PATENT OFFICE.

SAMUEL E. SHEPPARD, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

UTILIZATION OF BIOCHEMICAL LIGHT-SENSITIZING EXTRACTS IN THE ART OF PHOTOGRAPHIC MATERIALS.

No Drawing. Original application filed .Tune 6, 1924, Serial No. 718,410. Divided and this application filed January 21, 1926. Serial No. 82.845.

This application is a division'of my prior application 718,410 filed June 6, 1924 for.

art of light sensitive photographic materials, which has matured into Patent 1,574,- 943, granted Mar. 2', 1926.

This invention relates to the 'art of photographic materials.

One object of the invention is to provide photographic sensitizing materials capable of greatly increasing the light sensitiveness of photographic emulsions, especially of the developing-out type, even when inco- 0- rated therein in very small amounts. .nother-object is to provide such materials in a concentrated and highly purified condition; so that they will not impair or harmfully dilute the emulsions in which they are used. A still further object is to provide processes for obtaining said materials in said desirable condition.

Another object of the invention is to provide photographic emulsions, especially developing-out emulsions, having new and improved properties because of the use orpresence therein of my independent sensitizing. materials. Still another object'of my invention is to provide a process in which my said sensitizing materials are used to improve photographic emulsions, especially developing-out emulsions, as regards light sensitiveness, by which term I include their ability to give the earliest visible impression or image with the minimum exposure or'their ability to give density after a given exposure or both, the usual photographic fluid treatments being used in preparing such impression or image.

A further object of the invention is to provide colloid products, such as treated elatin, the usefulness of which for formmg light sensitive photographic emulsions, especially developing-out emulsions,

' greatly increased and -controlled by my said sensitizing'material incorporated therewith. Another object of the invention is to pro- 'videcorresponding processes 'for making saidintermediate colloidproducts.

Other objects are,to increase the sensitiveness of photographic emulsions, particularly developing-out ones, while wholly or partially dispensing with expensive or long A and uncertain so-called ripening methods;

particularlyistics of which have already been determined; to increase the general light-sensi tiveness of such photographic emulsions throughout the spectral ranges to which they are normally sensitive; to make such photographic emulsions of standard lightsensitive characteristics with gelatins which normally do not produce emulsions having such characteristics; to make, as intermediates in the manufacture of photographic emulsions, gelatins of standard light-sensitiveness giving power out of gelatins which do not normally have the power of giving such standard sensitiveness to emulsions, such as "developing-out ones, made from them. Further objects will hereinafter appear.

I have found photographic sensitizing materials, very small amounts of which greatly increases the light-sensitiveness of photographic emulsions, such as those of the developing-out gelatino-silver-halid type for example. These materials I am able to prepare in especially concentrated and purified forms, so that when incorporated in such emulsions or gelatins for such emulsions, they produce their sensitivity-increasing action without harmfully diluting said emulsions or gelatin or impairing the physical properties and purity of them. Consequently my sensitizing materials supply safe, dependable, and practically independent means for controlling the properties of'photographic emulsions in addition -to the customary expedients. The increases in sensitiveness o f-developing-out emulsions "appear upon the usual developing, fixing,

washing, and drying operations. Any customary developer, like the usual pyro or metol-hydrochinon alkaline developers, are suitable for example.

The active sensitizing body or bodies in my .sensitizing materials originate biochemically in plants. It is found for instance in especially useful quantities in the sterol-containing extracts or fractions of plant extracts; although said compounds may be even further purified and concentrated by whole or partial separation from the sterols. Fruitful and inexpensive souces of such active materials are by-products from cereal preparation, such as wheat, bran, rice hulls, peas, and beans. Of course, cereal grains and leguminous plant seeds, are only mentioned as illustrative of the many vegetable organic tissues from which my sensitizing materials may be prepared.

Different sources vary in the extent to which they contain sensitizing material; but their suit-ability can readily be determined by a simple test. A small sample of the source in question can be extracted by a method selected from the examples hereinafter given and the extract added to an emulsion such as one hereinafter described. If the sample sensitizing material 'sensitizmg compound which may be em-- causes a good increase in the light-sensitiveness of the emulsion, then the tested source can all be usefullyextracted. This extraction of a sample and trial in a known emulsion provides a ready test for raw-material; but the preferred sources listed hereinabove are in general reliable sources when a test is dispensed with. It 'is preferable to use sources which have not been submitted to excessive oxidizing action, which tends to destroy the sensitizing power of the material.

In preparing my sensitizing material, I free it from certain of its originally or normally associated impurities, especially the bulky ones, and thosewhich might impair or dilutephotographic emulsions. Generally speaking the preferred preparation of the material rids it of impurities insoluble in alcohol or those insoluble in light petroleum products such-as ligroin. These are typical of the many organic solvents of my ployed. When some of the solvent is to enter emulsion,- one is' selected which is substantially free from injurious action on the emulsion, alcohol being particularly good in this respect. My preferred preparation likewise frees the material from mineral compounds.

Idi nd upon separating the principal impurities from my sensitizing compounds that the resultinq materials prove to be in most cases sterol-containin fractions. Such a useful sensitizing stero extract is, for example, one substantially all soluble in alcohol or ligroin. In general these fractions are substantially free from Waterinsoluble impurities as well as free from at least part of the water-soluble but alcohol-insoluble or ligroin-insoluble impurities. The purified sensitizing compounds or bodies in dry form and paste form and in the form of solutions are capable of increasing the sensitiveness of photographic emulsions, when incorporated therein and so the term sensitizing material applies to any one of these forms.

\Vhile my invention is of wide utility in this art, it is especially useful in connection with gelatino-silver-halid emulsions suah, for example, as developing-out emulsions employed on negative or positive films, plates, papers, etc. The ammonia or alkaline type of such emulsions respond especially readily to my sensitizer. I shall, therefore, describe certain illustrative embodiments of my invention. in connection with such emulsions; but it will be understood that my invention is not restricted to these examples but can be embodied in many other species. i

In the following examples there will be described the preparation of my sensitizing material from vegetable sources. Wheat grains, corn, beans, peas, unhulled rice, wheat bran, mustard seeds, and rice bulls are a few illustration-s of the types available. Mustard seeds are the most fruitful source. They are preferably comminuted and then extracted. For instance, lima beans are first ground to a coarse flour,===- sufliciently fine to expose a large aggregate surface to the extractingliquid. This flour, without being stored'long enough to have its sensitizing material badly oxidized by the air, or volatilized, is extracted with ligroin boiling between and in a Soxhlet type of extractor until the operation is completed say for about 5 or 6 hours; although a longer time does no harm. For each kilogram (or 15,400 grains) of bean flour it is convenient to use 3 4; liters (or 56,600 mins.) of ligroin. The resulting extract is strong in sensitizing material and free from ligroiu-insoluble material. It is preferably evaporated to dryness and the residue taken up in alcohol, say 1 liter (or 17,000 mins.) for each 3 liters (or 56,600 mins.) of the original ligroin extract. lVhile the sensitizing material is thus finally dissolved in alcohol, it is free from its ligroin-insoluble originally associated im purities, because ligroin was used in the primary extraction.

Mustard seed, for another illustration, is a ground in water, allowed to ferment for overnight, or say 12 hours, at room temperature. Then the mash is extracted, say by shaking with ligroin. I I This solution is a strong sensitizing material but can lied still further, if saponifiable oils be present in troublesome amounts. To remove such oils there is added to each liter of the final alcoholic extract, about 300 cc. (or 5,100 mins.) of the alcoholic extract from 7 grams be concentrated and 'puri (or 108 grains) of sodium hydroxide. Of

' course, the strength of this. sappnifying alkaline solution can vary and 'equivalent solutions, like alcoholic potassium hydroxide be substituted. The mixture is boiled in apparatus having a reflux condenser, until the oils are saponified. The solution is then evaporated to dryness and the residue taken up in sufficient water for that urpose. Ligroin or related petroleum ether is added with shaking. The sensitizing material enters the ligroin while the saponified oils and any liberated glycerine stay inthe water. The ligroin extract is ,thenseparated out. It is convenient to use 661 cc. (or 11,220 mins.) of ligroin in this extraction 'for each liter (or 17,000 mins.) of alcoholic extract subjected to the saponification treatment. The ligroin is next evaporated OE and the residue taken up in alcohol, 330 cc.- (or 5,610 mins.) for each 660 cc. (or 11,220 mins.) of the ligroin from which the residue came. The finished alcoholic extract, which is likewise the sterol fraction from the beans,

' is a very powerful sensitizing material, purified" from fogging agents and from greasy or oily impurities. It is likewise substantially free from nitrogenous and mineral compounds.

The final alcoholic sterol extracts containing the sensitizing compounds, such as the extracts described above from vegetable sources are very useful but can' be purified or concentrated even further by removing the sterols, either wholly or partially. The sterols are substantially harmless to emulsions but are by themselves practically free from sensitizing actions,consequently their separation-1s useful. This can be done, for

example, by evaporating the sterol-contain-.

ing' fraction to dryness, taking up the dried residue in just enough warm but not boiling ethyl alcohol, say at to C., to dissolve it, cooling until sterol crystals form, removing said crystals, as by filtering, washing the crystals with a little ligroin, adding the wash liquid to the liquid from which the crystals came, and finally concentrating the combined liquids preferably under less than atmospheric pressure, by evaporation. Or the combined liquids can be evaporated to dryness and the residue containing the sensitizing compounds dissolved in alcohol. If thisfirst removal is insuflicient the process can be repeated. I

I My concentrated and purified sensitizing material whether in the form of a solution, a solid, or a paste is very powerful. Important and useful increases in light-sensitiveness of emulsions even occur when the actual sensitizing compounds or bodies in the sensitizing material are of the order of afifty-thousandth to a four hundred-thousandth of the weight of the emulsion in which they are incorporated. Of course,

amounts illustrate their and can be used when such are same wave len the sensitizing bodies can be incorporated in still larger proportions but these minute ower. Too much sensitizer tends to pr uce fog in some emulsions of the developing-out type. An excess should, therefore, be avoided. Usually thesolids in the added extract in its purified form are less than one ten-thousandth of the weight of the emulsion (nonaqueous ingredients).

My sensitizing material is concentrated and free from bulky and harmful impurities, 'with which it was originally or normally associated. In other words the ac-' tive sensitizing bodies are in general more concentrated and purer in my material than in the-sources from which they are derived. This makes it especially useful without either diluting them to an undesirable extent or introducing fogging or other harmful impurities. Stated in another way it increases theirlight-sensitiveness without deteriorating their other qualities, such as setting ability, melting point, viscosity, and grain-characteristics. tablish a ratio of sensitizing material to silver halid in the emulsions which is independent of the ratio of gelatin to silver halid.

ear to be not truly soluble in water but to orm colloidal solutions therein. Its solu- It enables me to es- The'sensitizing bodies in my material aptions in alcohol and ligroin are true ones.

My sensitizing material has a very useful stability provided excessive exposure to 0x1- dizing influences is not allowed. It 1 s generally neither markedly acid or alkaline although it withstands dilute acid and alkalis resent 1n the emulsions. Since it is substantially without fogging action on emulsions when used in the proper amount for sensitizing them it yields emulsions of surprising stabihty when their sensitiveness is considered, foggip being long delayed. I classify the matena as biochemical or organic in distinction from inorganic materials such as ammonia and silver nitrate for example. The alcoholic solutions are, of course, protected from v action, the alcohol being provided harmful dilution is corresponding to the spectral absorption of the sensitizing material. My material. is effective in increasing the general lightsensitiveness of orthochromatic, panchromatic, X-ray, and all special emulsions, as well as the ordinary or non-color sensitized ones. .t can be added with dyes or before or after them. It is nearly colorless itself. It is preferably added separately or independently of the sensitizing dye, generally but not necessarily before any dye. It is especially effective in emulsions having, at least, slight alkalinity.

My sensitizing'material may be used in many ways. Broadly it may be incorporated in emulsions or in colloids for emulsions or both. It can also enter the emulsion mixed with other ingredients thereof whether organic or inorganic. It gives added light-sensitiven'ess to various emul sions having different speeds and other distinctive characteristics. While it may be added at different stages of emulsion manufacture, nevertheless, it can be very conveniently mixed into the emulsion when the latter is otherwise complete ready for coating. Since its action is immediate when incorporated, the coating need be delayed onlylong enough to mix in the sensitizing material. With the grain characteristics. such as size distribution etc. already determined, and the other physical and photographic properties of the emulsion already taken care of at this stage, I can practically independently increase its light-sensitiveness without impairing said other properties by adding my concentrated purified sensitizing gmaterial. 7

As will be clear to those skilled in this art, the proportion of sensitizing material added to the emulsions will vary according to the concentration of the sensitizing material and according to the increase in light-sensitlveness which is desired. The alcoholic extracts hereinabove described can be added, as a basis for trial, in the proportion of from 10 to 25 parts of extract to 1000 parts by volume of the emulsion. This is of the order of magnitude of 2 per cent. Ofcourse, larger proportions can be used,

smaller amounts can be used for slight increases in sensitiveness an more concentrated extracts can be employed, or even the dried residues therefrom.

Where different batches of emulsion fall below a required manufacturing standard of ii ght-sensitiveness, although they may be .otherwise satisfactory, their sensitiveness can readily be brought up to standard by mixing in my sensitizing material, the proportion varying with the increase necessary to produce a. uniformproduct. Emulsions having almost no practical light-sensitiveness but having enough other desirable avoided;

' cess potassium halids.

qualities can be made usefully light-sensitive my material. Thus the latter is useful 1n connection with emulsions having good initial light-sensitiveness and those having almost no 1n1t1al scnsltiveness. The

increase in scnsitiveness can be effected in one step by thoroughly stirring all of the sensitizing material into the emulsion at one time; or it may be incorporated ,part at a time in successive steps.

The following example illustrates how light-sensitive photographic emulsion may be prepared and improved by the aid of my sensitizing material. Of course, my invention is not restricted to this illustration but is applicable in the cases of the very large number of widely different emulsions in this art. The emulsion forming operations hereinafter described are along the lines of known practice, see for instance Die photographic mit bromsilber gelatine by J. M. Eder, publishcdin Halle, Germany in 1903 by lVilhelm Knapp as Part III of Eders Ausfuhrlichcs Handbuch der Photographic.

The two following solutions are made up, the parts being by weight:

(A) 900 parts of silver nitrate in 9,200 parts of water.

(B) 690 parts of'potassium bromide and 50 parts of potassium iodide in 6,100 parts of water along with 300 parts of gelatin.

In mixing B, the-halid salts are first dissolved the water and the gelatin then added to the salt solution. Solution B is then warmed, say to 140 F. or 150 F. for example; and the silver nitrate solution A is gradually added to it with constant stirring. Itispr'eferable to warm solution A before adding it to B, say to 150 F. or 160 F. for instance. lvhen solution A has been thoroughly incorporated in solution B, there are then added 43 parts of strong ammonia previously dissolved in 900 parts of water. The emulsion formed by these operations is allowed to stand for a short time, say 15 minutes to a half hour for example. Then 1050 parts of gelatin are dissolved in it with thorough mixing. The emulsion is next cooled, such as by keeping in a cool space, until it, setsto a firm jelly. The latter is broken up, as by shredding, for instance, and thoroughly washed to remove soluble salts, such as potassium nitrate and any ex- The wash water is, of course, cool enough notto melt the pieces of emulsion jelly. The washed emulsion is next remelted to 100 F. and 1050 parts of water soaked gelatin are thoroughly mixed into it, the temperature then beingraised, say between 120 F. and 150 F.,'for instance, for a short time, say a few minutes. It is then cooled and set. It is of the ammonia or alkaline type of emulsion.

My sensitizing material may be. usefully incorporated at any stage of theabove descr1bed process of preparing the emulsion, even being premixe with solutions A. or B "or with ammonia or with the gelatin, at the it 25 parts by volume of my sensitizing mathe desired flowabilit is fiim,

terial (say one of the alcoholic extracts described above) for each 1000 parts by volume of emulsion. Since the actual sensitizing bodies are in the colloidized solids in such preparation and since such solids total as only a small proportion of said preparation (generally far less than one twenty-fifth) it follows that the actual sensitizing bodies are very useful when added in even less than one art per thousand of emulsion by weight. ften the ratio is less than one in ten-thousand or one in one-hundred-thousand. It will be noted that this addition does not substantially dilute the emulsion, being of the order of two per cent.

With its light-sensitiveness increased by my material, the emulsion, being melted to coated on its support, such as glass, paper, etc., in the well known way. It is convenient to con-- trol and check the process by coating samples of the emulsion before and after the addition of my sensitizing material, the coated s ecimens being tried out photographica ly by any well known sensitometric test, or even by comparative camera exposures on the same subject, under like conditions. Qf course, the usual precautions are observed during the emulsion making and coating processes such as the use of nonactinic or safe light, cleanness of vessels and air, etc.

The difierent gelatins sold for photographic emulsion-making may be used in the example 'ven above, hard ones being very useful. he temperatures given, are, of course, adjusted if the particulargelatin employed has physical properties, such as melting and setting points, which deviate considerably from the usual ones, such adjustment being a matter of routine control.

Instead, however, of using gelatins which give emulsions 'of useful but lower sensitiveness even before the addition of my sensitizing material, an almost inert gelatin may be em loyed,one which forms an emulsion which produces a developable image only after impractically long exposures, and then does not yield an ima e of desirable density. A gelatin which orms such a nearly inert emulsion maybe prepared in the way described under the heading Preparation of ash-free gelatin in pages 1856 and 1859 of the Journal of the emulsions are to be made.

American Chemical Society, September, 1922, Vol. XLIV, No. 9, being article by Sheppard, Sweet an Benedict on Elasticity of purified gelatin jellies as a function of hydrogen-ion concentration. Emulsions of impractically low-light-sensitiveness made by the above described processfrom such prepared gelatin, are transformed by my sensitizing material into emulsions which give developable images of exposures. I have, for example, been able to increase the light-sensitiveness of such low sensitive emulsion over twenty times, the exposures for a given subject being cut to less than one-twentieth of the original one and the image density being made excellent.

art of an by a corresponding gain. Usually the percentage increase in light-sensitiveness is at least ten times the percentage increase in volume of the emulsion caused by the addition of material producing said increases. Often it is very much more indeed. Increases of the same general order of magnitude are made when my sensitizing material is added in similar proportions to emulsions which are made from normal photogra hic gelatins or mixtures of such norma gelatins with said almost inert gelatins, and already haveuseful, but lower initial sensitiveness. Different percentages of sensitizer produce correspondingly different increases. The increases in developing-out emulsions ap ear upon the usual develop-ing, fixing, was ing and drying operations.

For testing the-power of sensitizing material, an almost inert emulsion made, as above described from said prepared gelatin is also very useful. Ten to twenty-five parts by volume of the sensitizing liquid can be added to 1000 parts of such emulsion and the mixture coated and tested photographically incomparison with a parallel sample of the unsensitized emulsion. While the addition of sensitizing material as a liquid is most convenient, the residue obtained from evaporating off the water from said liquid can be added directly to the emulsion. But a liquid spreading agent is preferable. In addition to having increased sensitiveness, emulsions containing my sensitizing material have improved stability or keeping qualities because of the purifi cation of said material. Y

My sensitizing material may be incor rated into gelatin with which photograp ic This strengthened gelatin then constitutes a valuable intermediate in emulsion manufacture. For example, the gelatin can be melted and to parts by volume of my above described aqueous sensitizing material can be thoroughly mixed into 1000 parts of gelatin.

Emulsions made from the mixture have increased light-sensitiveness as compared with F 75 cellent density after usefully brief exthem may be omitted. In other words, my

sensitizing material acts by itself to increase the light-sensitiveness, whether ripening stepsbe employed or not, and so can wholly or partially replace them. The efi'ect of either or both of such steps, however, is to help increase the light-sensitiveness otthe emulsions and thus give a stronger initial sensitized condition which is multiplied or increased by using my sensitizing material." When using the ash-free gelatin mentioned above, they are especially readily dispensed with; but if retained in making very sensitive emulsions, they can be shortened and made more certain in effect by reasonof the use of my powerful and dependable sensitizing material. I consider the materials containing said compounds to be concentrated when they give a useful sensitizing effect without harmfully diluting the emulsions. My materials do not act as a photographic developer.

have described gelatin emulsions because at the present time they are the ones which have the widest practical use. Moreover they form the best medium for testing my sensitizing materials, the characteristic action of such materials on such emulsions being one of the best identifying criteria of such sensitizing materials. Other organic colloids and mixtures of them with each other or with gelatin, where their nature admits such mixtures,'may be used in making light-sensitive emulsions which can be improvedby adding my sensitizing material. Albumens, agar-agar, gums, such as gumarabic, cellulosic derivatives such as collodion are instanced. While I have disclosed the use or my sensitizer in connection with such sensitive substances as silver bromide and silver iodide, other light-sensitive substances can be employed, such as silver chlorid, alone or mined with one or more of the others.

Having thus described my invention, what I claim a j w and desire to'secure by L ti Patent is:-

1. photographic sensitizing material compris ng. asterol-containing fraction of a biochemical-extract dissolved in ligroin and having the property of'increasing the gengraphic ligroin-insoluble originally associated impurities. i

- 3. A. photographic gelatino-silver-halid emulsion comprising gelatin, silver halid particles suspended therein, and an independent biochemical sensitizing extract, substantially free from its originally associated ligroin-insoluble impurities, upon which extract at least part of the light-sensitiveness of said emulsion depends, the physical properties of said emulsion corresponding to the physical properties of said gelatin being substantially unaltered by said sensitizing extract.

- 4. In the process of making a photographic gelatino-silver-halid emulsion, extracting a biochemical sensitizing material with lig: roin, and incorporating said extracted material in said emulsion to increase the lightsensitiveness thereof.

5. An intermediate for use in the making of photographic emulsions comprising an emulsion-forming colloid and an independent biochemical sensitizing material incorporated therein, said material being substantially free from its normally-associated ligroininsoluble impurities, said intermediate having the propert of forming emulsions of higher general light-sensitiveness than those formed under parallel conditions from said a colloid without said material.

6. A biochemical sensitizing material which has the property of increasing the light-sensitive-ness of photographic gelatinosilver-halid emulsions when incorporated therein, said material being substantially free from its normally associated waterinsoluble impurities and at least part of its normally associated water-soluble but ligroin-insoluble impurities.

. 7. In the process of preparing, from plant tissue containing the same, a sensitizing material havin the property of increasing the general lig t-sensitiveness of photogelatino-silver-halid emulsions when incorporated therein, the step of extracting said tissue with a solvent of said material in which the-bulk of said tissue is substantially'insoluble, and incorporating suflicient of said material in such an emulsifon to increase the light-sensitiveness there- 0 ing the concentrated extract in such emulsion to increase the general light-sensitiveness thereof.

9. In the process of preparing, from seedy tissues, a sensitizing material which has the property of increasing the general light-sensitiveness of photographic gelatinosilver-halid emulsions in which it is incorporated, the step of extracting said material from said tissues into an organic liquid which is a stronger solvent of said material than of the bulk of said tissues, and incorporating suflicient of said material in such an emulsion to increase the liglit-sensitiveness thereof.

. 10. In the process of preparing, from speedy tissues, a sensitizing material which has the property of increasing the general light-sensitiveness of photographic gelatinosilver-halid emulsions when incorporated therein, the step of extracting said material from said tissues with an organic solvent which is without substantially injurious action on said emulsions, and incorporating sufiicient of said material in such an emulsion to increase the light-sensitiveness there- 11. In the process of making a photographic emulsion containing a biochemical colloid, extracting from active plant tissue a sensitizing material difl'erent from said colloid and incorporating suflicient of said material in said emulsion to increase the gen- Qital light-sensitiveness thereof.

12-. In the process of making a photographic gelatino-silver-halid emulsion, ex-

tracting from active plant tissue by an organic solvent a sensitizing material and incorporatin sufiicient of said material in said emulsion to increase the light-sensitiver-ess thereof.

13. In the process of making a photo.- graphic emulsion containing a biochemical colloid, extracting a sensitizing sterol fraction independent of said colloid from a plant source and incorporating said fraction in said emulsion to increase the light-sensitiveness of the latter.

14. In the process of making a photographic emulsion containin a biochemical colloid, extracting from see y tissue a sensitizing material and incorporating in said emulsion suificient of said material to increase the light-sensitiveness thereof.

15. In the process of making a photographic biochemical colloid-sensitive-silversalt emulsion, extracting a sensitizing material from seedy tissue in an organic solvent and incorporating said material in said emulsion.

16. In the process of making a photographic gelatino-silver-halid emulsion, ex-

tracting sensitizing material from seedy tissue, concentrating thev extract, and incorporating it i i-said emulsion.

17. In the process of making a photographic gelatino-silver-halid emulsion, extractin a sentizing material from seedy tissue in an organic solvent which is substantially without injurious action on said extract in said emulsion to increase the general light-sensitiveness thereof.

18. In the process of making a photographic emulsion containing a biochemical colloid, separatin a sensitizing material from its associate seed tissue and incorporating it in said emulsion.

Signed at Rochester, New York this 18th day of January 1926.

SAMUEL E. SHEPPARD. 

